1. Field of the Invention
This invention relates to the field of dual stage actuated suspensions for hard disk drives. More particularly, this invention relates to the field a dual stage actuated suspension having channels to control the overflow of adhesive used to affix microactuators to the suspension.
2. Description of Related Art
Magnetic hard disk drives and other types of spinning media drives such as optical disk drives are well known. FIG. 1 is an oblique view of an exemplary prior art hard disk drive and suspension for which the present invention is applicable. The prior art disk drive unit 100 includes a spinning magnetic disk 101 containing a pattern of magnetic ones and zeroes on it that constitutes the data stored on the disk drive. The magnetic disk is driven by a drive motor (not shown). Disk drive unit 100 further includes a disk drive suspension 105 to which a magnetic head slider (not shown) is mounted proximate a distal end of load beam 107. The “proximal” end of a suspension or load beam is the end that is supported, i.e., the end nearest to base plate 12 which is swaged or otherwise mounted to an actuator arm. The “distal” end of a suspension or load beam is the end that is opposite the proximal end, i.e., the “distal” end is the cantilevered end.
Suspension 105 is coupled to an actuator arm 103, which in turn is coupled to a voice coil motor 112 that moves the suspension 105 arcuately in order to position the head slider over the correct data track on data disk 101. The head slider is carried on a gimbal which allows the slider to pitch and roll so that it follows the proper data track on the disk, allowing for such variations as vibrations of the disk, inertial events such as bumping, and irregularities in the disk's surface.
Both single stage actuated disk drive suspensions and dual stage actuated (DSA) suspension are known. In a single stage actuated suspension, only voice coil motor 112 moves suspension 105.
In a DSA suspension, as for example in U.S. Pat. No. 7,459,835 issued to Mei et al. as well as many others, in addition to voice coil motor 112 which moves the entire suspension, at least one microactuator is located on the suspension in order to effect fine movements of the magnetic head slider to keep it properly aligned over the data track on the spinning disk. The microactuator(s) provide much finer control and much higher bandwidth of the servo control loop than does the voice coil motor alone, which effects relatively coarse movements of the suspension and hence the magnetic head slider. A piezoelectric element, sometimes referred to simply as a PZT, is often used as the microactuator motor, although other types of microactuator motors are possible.
FIG. 2 is a top plan view of the distal end of a suspension in which the PZTs are mounted at the gimbal end of the suspension, according to a previous design by the assignee of the present application. No representation or admission is made herein that that design is “prior art” to the present application within the legal meaning of that term. In the design, a microactuator 18 such as a PZT microactuator is bonded at its proximal side to a relatively fixed portion of the suspension including the flexure, and is bonded at its distal side to stainless steel finger 12 that extends from the gimbal on which magnetic read/write head 14 is mounted. As PZT 18 expands and contracts, that expansion/contraction pivots the suspension gimbal from side to side thus effecting fine lateral movements of a transducer head 14, which is usually a read/write head. The lateral movements of transducer head 14 constitute radial movements of transducer head 14 relative to the spinning data disk platter 101.
FIG. 3 is a cross section view of the suspension of FIG. 2, taken along section line 3-3 and showing the details of how PZT 18 is mounted at its proximal end to the relatively fixed part of the suspension, and more specifically to a relatively fixed part of the flexure. The flexure includes a support layer 20 such as stainless steel, an insulating material 22/24 such as polyimide, and a signal conductor such as copper or copper alloy 26. A void or gap 23 is formed in the polyimide 22/24, to create what is effectively a containment vessel into which a non-conductive adhesive such as non-conductive epoxy 30 is dispensed, the non-conductive epoxy 30 being contained by first polyimide section 22 on one side, second polyimide section 24 on a second side, and stainless steel support layer 20 on the bottom. Conductive epoxy 34 is dispensed so as to form a conductive bridge from copper contact pad 26 which is part of the signal conductor layer to the top surface of PZT 18 which is metallized to constitute an electrode. Second polyimide section 24 thus forms not only one side of an epoxy containment vessel, but also acts as an insulation layer that prevents the bottom surface of PZT 18 from electrically shorting to stainless steel 20.
Although it is contemplated that copper contact pad 26 will normally provide the driving voltage for PZT 18 on its top surface, and a ground potential lead (not shown) will normally be electrically connected to the bottom surface of the PZT, it is not necessary that the drive voltage is on top and the ground is on bottom. Those positions could be reversed, with copper contact pad 26 providing the ground potential to the top surface of PZT 18 and the driving voltage being connected to the bottom surface of the PZT.